shapefiles to nice Bézier curves

Dennis McClendon

Posted 17 June 2010 - 02:10 PM

Dennis McClendon

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I'm starting a new street mapping project and there's nice local GIS data available. But it's a modern suburban area with lots of gently curving streets, so I hate to have Illustrator lines with 300 points instead of nice smooth Bézier curves with three points. How do I proceed? Can Indiemapper help?

Charles Syrett

Posted 17 June 2010 - 02:30 PM

Charles Syrett

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I'm curious too, since I'm planning to start shifting to Ily soon. (In FH it's a no-brainer: use Smooth Xtra to add beziers, then simplify lines.) How are people doing this with MAPublisher, and without it?

Posted 17 June 2010 - 03:00 PM

Illustrator will convert your straight lines to bezier curve when you use the simplify command [object] > [path] > [simplify]

Use a very high curve precision like 99% to maintain the most accuracy while converting hard edges to smooth curves. Do not check the straight lines option. Simple.

If you have lines or polygons of different overall shape and size that share an edge be aware that the Illy simplify command will change the paths such that they no longer match each other, especially if you go lower than 99% 98% precision. You can maintain topology and get more smoothing if you have MAPublisher. Use the MAPub simplify command to weed out the extra points and then use a 99% Illy simplify to convert to bezier curve.

Illustrator will convert your straight lines to bezier curve when you use the simplify command [object] > [path] > [simplify]

Use a very high curve precision like 99% to maintain the most accuracy while converting hard edges to smooth curves. Do not check the straight lines option. Simple.

If you have lines or polygons of different overall shape and size that share an edge be aware that the Illy simplify command will change the paths such that they no longer match each other, especially if you go lower than 99% 98% precision. You can maintain topology and get more smoothing if you have MAPublisher. Use the MAPub simplify command to weed out the extra points and then use a 99% Illy simplify to convert to bezier curve.

I do this at 99%, and then repeat at 99% 10-15 times if necessary, or Ctrl+d over and over until I get the smooth flow that I want.

Oh yeah, I also use Swiss Cartography script/plug-in when I finish simplifying the path. I think the command is fix bezier curves and curves. kru

"Ah, to see the world with the eyes of the gods is geography--to know cities and tribes, mountains and rivers, earth and sea, this is our gift."Strabo 22AD

ALSO, we've developed some ArcGIS tools here in Zurich to make it very easy to do this processing interactively (and without Geoprocessing). As pointed out above, different features can require different simplify/smooth parameters, and it can be an interactive process. The Line-to-Curve tool makes it easy and fast to simplify/smooth one, several, or many lines/polygons.

We have tools that go in the reverse direction (Curve-to-Line and Densify-Line). Our Swiss cartographer customers use the tools to work with line/polygon geometry in "bezier mode", and then convert back to simple line geometry. Some GIS DBAs don't like curves in their data!